Testicular tumor tissue from androgen insenstive male pseudohermaphrodite rats will be cultured without and in the presence of luteinizing hormone, prolactin, estrogen, and prolactin and estrogen together. This should determine what effect these substances have on the growth of such tumors. Testes of tfm rats lack 17-ketoreductase (Endocrinology 94:1). Since it is present in normal rats, an attempt will be made to determine to what extent testicular tissue from normal rats may have an inductive action influencing the growth rate of testicular tumor tissue from tfm rats when grown together in the same culture medium. This may give another clue to any role played by this enzyme in the sequence of events responsible for testicular tumors in tfm rats.